Rascoe Philip A, Cao Xiaobo, Daniel Jonathan C, Miller Steven D, Smythe W Roy
Department of Thoracic and Cardiovascular Surgery, The University of Texas M.D. Anderso Cancer Center, Houston, TX 76508, USA.
J Thorac Cardiovasc Surg. 2005 Aug;130(2):393-400. doi: 10.1016/j.jtcvs.2004.11.029.
The phosphoinositide-3 kinase signaling pathway is implicated in the development of malignancy and promotes cell-cycle progression and resistance to apoptosis. Malignant mesothelioma tumor specimens demonstrate high levels of the phosphoinositide-3 kinase downstream mediator phosphorylated Akt. Exposure of mesothelioma cell lines to LY294002, a phosphoinositide-3 kinase inhibitor, results in apoptotic cell death and decreased phosphorylated Akt in vitro and tumor burden reduction in vivo. Phosphoinositide-3 kinase is activated by cell-surface receptor tyrosine kinases. We sought to determine which receptors are present in mesothelioma and their role in cellular survival and phosphoinositide-3 kinase signaling.
Western blot analysis was performed to determine the relative expression of epidermal growth factor receptor, insulin-like growth factor receptor, and platelet-derived growth factor receptor in the mesothelioma cell lines I-45 and REN and the mesothelial line Met5a. After exposure of mesothelioma lines to kinase inhibitors, a cell viability assay was performed, cell-cycle analysis was performed to determine the percentage of apoptosis, and Western blot analysis was performed for phosphorylated Akt.
Inhibition of epidermal growth factor receptor resulted in apoptotic cell death and Akt hypophosphorylation in mesothelioma cell lines. Insulin-like growth factor receptor inhibition led to apoptotic cell death without affecting Akt phosphorylation. Platelet-derived growth factor receptor inhibition did not affect cellular survival or phosphoinositide-3 kinase signaling.
In malignant mesothelioma constitutive activation of phosphoinositide-3 kinase/Akt results in cellular survival and contributes to the malignant phenotype. We have demonstrated that epidermal growth factor receptor inhibition leads to apoptotic cell death through downregulation of phosphoinositide-3 kinase signaling in mesothelioma cell lines, whereas insulin-like growth factor receptor inhibition leads to apoptosis independent of phosphoinositide-3 kinase. Epidermal growth factor receptor, insulin-like growth factor receptor, and phosphoinositide-3 kinase inhibition might be clinically relevant in malignant mesothelioma.
磷酸肌醇-3激酶信号通路与恶性肿瘤的发生发展相关，可促进细胞周期进程并增强细胞对凋亡的抵抗能力。恶性间皮瘤肿瘤标本显示磷酸肌醇-3激酶下游介质磷酸化Akt水平较高。将间皮瘤细胞系暴露于磷酸肌醇-3激酶抑制剂LY294002后，在体外可导致凋亡性细胞死亡并降低磷酸化Akt水平，在体内可减轻肿瘤负荷。磷酸肌醇-3激酶由细胞表面受体酪氨酸激酶激活。我们试图确定间皮瘤中存在哪些受体及其在细胞存活和磷酸肌醇-3激酶信号传导中的作用。
采用蛋白质印迹分析来确定表皮生长因子受体、胰岛素样生长因子受体和血小板衍生生长因子受体在间皮瘤细胞系I-45和REN以及间皮细胞系Met5a中的相对表达。将间皮瘤细胞系暴露于激酶抑制剂后，进行细胞活力测定、细胞周期分析以确定凋亡百分比，并对磷酸化Akt进行蛋白质印迹分析。
抑制表皮生长因子受体可导致间皮瘤细胞系凋亡性细胞死亡和Akt去磷酸化。抑制胰岛素样生长因子受体可导致凋亡性细胞死亡，但不影响Akt磷酸化。抑制血小板衍生生长因子受体不影响细胞存活或磷酸肌醇-3激酶信号传导。
在恶性间皮瘤中，磷酸肌醇-3激酶/Akt的组成性激活可导致细胞存活并促成恶性表型。我们已证明，抑制表皮生长因子受体可通过下调间皮瘤细胞系中的磷酸肌醇-3激酶信号传导导致凋亡性细胞死亡，而抑制胰岛素样生长因子受体可导致与磷酸肌醇-3激酶无关的凋亡。抑制表皮生长因子受体、胰岛素样生长因子受体和磷酸肌醇-3激酶在恶性间皮瘤中可能具有临床相关性。
